A novel detection procedure for mutations in the 23S rRNA gene of Mycoplasma pneumoniae with peptide nucleic acid-mediated loop-mediated isothermal amplification assay

Rapid and easy detection of a single nucleotide point mutation of bacterial genes, which is directly linked to drug susceptibility, is essential for the proper use of antimicrobial agents. Here, we established a detection method using a peptide nucleic acid mediated loop-mediated amplification (LAMP) assay for macrolide (ML)-susceptible Mycoplasma pneumoniae. This assay specifically detected the absence of missense mutations encoding the central loop of domain V in the gene encoding 23S rRNA, which can reduce the affinity for MLs and subsequently generate ML-resistant strains of M. pneumoniae. Reactions were performed at 62 degrees C for 60 min and targeted gene amplifications were detected by real-time turbidity with a turbidimeter and naked-eye inspection of a color change. The assay had an equivalent detection limit of 100.0 fg of DNA with the turbidimeter and showed specificity against 54 types of pathogens, whereas amplification was completely blocked, even at 100.0 pg of DNA per reaction, in the presence of point mutations at 2063A and 2064A. The expected LAMP products were confirmed through identical melting curves in real-time LAMP procedures. This method would be a simple and rapid protocol for single nucleotide polymorphism genotyping as point of-care testing technology without amplification of the sequences carrying the point mutations 2063A and 2064A in ML-resistant M. pneumoniae strains.